package demoTest;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


//点击下载调用提交的servlet

public class DownLoadServlet extends HttpServlet{
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
			//得到要下载的文件名
			String fileName = request.getParameter("filename"); //23239283-92489-阿凡达.avi   此处正常
		//	fileName = new String(fileName.getBytes("iso8859-1"),"UTF-8");//处理完是文件名乱码？？？是不是上传已经设置过
			//上传的文件都是保存在/WEB-INF/upload目录下的子目录当中
			String fileSaveRootPath=this.getServletContext().getRealPath("/WEB-INF/upload");
			//通过文件名找出文件的所在目录
			String path = findFileSavePathByFileName(fileName,fileSaveRootPath);
			//得到要下载的文件
			File file = new File(path + "\\" + fileName);//中文名乱码
			//如果文件不存在
			if(!file.exists()){
			request.setAttribute("message", "您要下载的资源已被删除！！");
			request.getRequestDispatcher("/jsp/message.jsp").forward(request, response);
			return;
			}
			//处理文件名
			String realname = fileName.substring(fileName.indexOf("_")+1);
			//设置响应头，控制浏览器下载该文件
			response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(realname, "UTF-8"));
			//读取要下载的文件，保存到文件输入流
			FileInputStream in = new FileInputStream(path + "\\" + fileName);
			//创建输出流
			OutputStream out = response.getOutputStream();
			//创建缓冲区
			byte buffer[] = new byte[1024];
			int len = 0;
			//循环将输入流中的内容读取到缓冲区当中
			while((len=in.read(buffer))>0){
			//输出缓冲区的内容到浏览器，实现文件下载
			out.write(buffer, 0, len);
			}
			//关闭文件输入流
			in.close();
			//关闭输出流
			out.close();
			}
			 
			/**
			* @Method: findFileSavePathByFileName
			* @Description: 通过文件名和存储上传文件根目录找出要下载的文件的所在路径
			* @Anthor
			* @param filename 要下载的文件名
			* @param saveRootPath 上传文件保存的根目录，也就是/WEB-INF/upload目录
			* @return 要下载的文件的存储目录
			*/
			public String findFileSavePathByFileName(String filename,String saveRootPath){
			int hashcode = filename.hashCode();
			int dir1 = hashcode&0xf; //0--15
			int dir2 = (hashcode&0xf0)>>4; //0-15
			String dir = saveRootPath + "\\" + dir1 + "\\" + dir2; //upload\2\3 upload\3\5
			File file = new File(dir);
			if(!file.exists()){
			//创建目录
			file.mkdirs();
			}
			return dir;
			}
			 
			public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
			doGet(request, response);
			}}
